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But we also lie naturally and instinctively, as a way to manage and control our relationships, to protect our partners and our families, and to keep our options open.
In fact, we lie so much and for so many reasons that often we don't even think of it as lying at all, but as 'relationship management'. Those simple, altruistic lies such as saying we've had a lovely time when we haven't, that someone looks nice when she doesn't, or that we're delighted with a gift we don't really like, are just some of the small ways that lying oils the wheels of our social lives, keeps the peace, and makes other people happy.
There is something particularly humiliating for a man about being made a cuckold.
So we lie to protect ourselves from the judgments of others, and because sexual 'reputation' still matters more to women, whether we like it or not.
They live, psychologically, in the moment, while women think around corners and two steps ahead.' We're also better at mental multi-tasking.
'You can keep all the different strands of a lie in your minds, remember them and make them convincing.' Men lie, too, but they are much more likely to forget something, or make a mistake and get caught out.
'My mother always used to say that you should never tell a man everything,' says Clare, 38, 'and I thought it was rubbish. 'I don't have a secret account, but I'm not completely honest about how much money I spend. 'Women are better liars because they're more psychologically sophisticated,' says Dr Holmes.
'You can argue about whether it's nature or nurture, but women are programmed to be much more relationship and people orientated than men.
But Brian was a permanent "man-child" - a great lover, but not the kind of man you'd marry.
Mobile phones, internet chat rooms and email also make it easier to fuel intimate encounters.
But while women's lives and sexual behaviour might have changed, their willingness to be honest about it hasn't.
It's not just a question of avoiding the inevitable row over the 'worth it' factor of a pair of killer heels, but of holding something back in order to maintain a sense of emotional independence, and to balance out the power we might feel our partner has in other aspects of the relationship. Why have a huge row over something he needn't even know about?
A recent survey by a leading building society also found that women are much more likely than men to have a 'secret' account with money their partner knows nothing about. I never tell him about my girlfriends' secrets, because he'd be judgmental and disapproving. But it's easy to see how a climate of withholding and keeping smaller secrets can easily lead to bigger ones.